ZonePlugin

Gather content of a page in named zones while rendering it

The primary purpose of ZonePlugin is to streamline the anatomy of a HTML page in a way to allow today's browsers to process it more efficiently. Page loading time has been reported to decrease significantly when all JavaScript files are removed from the HEAD element and appended to the end of the BODY element of a page. That's because the browser will stop processing a page as soon as a JavaScript file is found in the linear order of the page. The browser will only proceed after this file has been downloaded and excecuted. Notably other content like CSS files and image material will not be downloaded in parallel as long as the JavaScript interpreter hasn't finished.

Currently, Foswiki uses ADDTOHEAD to place additional CSS and JS files into the HEAD element. It does not reorder those files in any way other than specified by the explicit requires argument to the macro. Further more, it is only able to add stuff to one specific location of a HTML page, the HEAD element.

By using ADDTOZONE CSS and JS material can be added to the resulting page incrementally while the core engine parses templates and wiki applications. ADDTOZONE's first parameter is the name of the zone to add stuff to. There are two special zones: body and head. All CSS should be added to the head zone while all JS goes into the body zone.

The actual location of a zone is specified with an explicit RENDERZONE macro. This macro expands to the content of all material that has been posted to the named zone. Note, that this happens at the very end of the rendering pipeline of Foswiki. That means RENDERZONE is not processed as a normal macro obeying the evaluation order of the TML parser. Instead, all calls to ADDTOZONE are processed by the TML parser first after which all zones are expanded.

If RENDERZONE{head} and RENDERZONE{body} aren't found in the final page explicitly, they are expanded at the appropriate position, that is at </head> and </body> respectively.

The features of this plugin have been proposed as a core feature for Foswiki to replace the standard ADDTOHEAD with the more generic ADDTOZONE tag. This plugin allows authors of extensions and wiki applications to make use of this advanced feature in a backwards-compatible way. As soon as the ADDTOZONE macro has been released as part of newer Foswiki versions, this plugin won't be of use anymore.

WARNING: Using this plugin can potentially break your installation. If you experience occasional JavaScript errors, switch off OptimizePageLayout in configure. This mode will render the HTML page in a non-optimized way similar to how the standard ADDTOHEAD mechanism does.

In any case is it recommended to use ADDTOHEAD or ADDTOZONE to properly add this code to the page. It is not recommended to add JavaScript code otherwise.

If you rely on having JavaScript added to the page without using ADDTOHEAD or ADDTOZONE then you have to disable OptimizePageLayout mode most probably. In this case the HTML page cannot be optimized.

ZonePlugin will try to detect whether any use of ADDTOHEAD contains text/javascript and automatically move its content to the body zone while adding anything else to the head zone.

Syntax

ADDTOZONE 

%ADDTOZONE{
  "zone"
  ...
}%

Note, that using topic and section is actually a short form of 

%ADDTOZONE{
   "myzone"
   text="$percntINCLUDE{\"topic\" section=\"section\" warn=\"off\"}$percnt"
}%

See also VarRENDERZONE

RENDERZONE 

%RENDERZONE{"zone" ...}%

Note, that you can create as many zones as you like. The plugin does not restrict you to use it only for body and head. Interesting use cases in wiki applications:

See also VarADDTOZONE

Perl API

This plugin patches the Foswiki::Func API for backwards compatibility.

The latter will try to detect text/javascrtipt and move content into the body zone. Otherwise, it will be added to the head.

Any use of ADDTOHEAD or Foswiki::Func::addToHEAD() will emit a warning to the log files (must be switched on with the Warnings flag in configure). This can be used to hunt down suboptimal use of these APIs.

Installation Instructions

You do not need to install anything in the browser to use this extension. The following instructions are for the administrator who installs the extension on the server.

Open configure, and open the "Extensions" section. Use "Find More Extensions" to get a list of available extensions. Select "Install".

If you have any problems, or if the extension isn't available in configure, then you can still install manually from the command-line. See http://foswiki.org/Support/ManuallyInstallingExtensions for more help.

Author(s): Michael Daum
Copyright: © 2010 Michael Daum http://michaelaumconsulting.com
License: GPL (Gnu General Public License)
Release: 2.1
Version: 6966 (2010-03-28)
Change History:  
28 Mar 2010 fix problem where Foswiki 1.0.x installations would fail with "Undefined subroutine &Foswiki::Func::addToZone"
26 Mar 2010 suppressing plugin initialisation on Foswiki engines >= 1.1; renamed BackwardsCompatible switch to OptimizePageLayout (defaults to off)
19 Feb 2010 added {BackwardsCompatible} switch
15 Feb 2010 be more careful applying the monkey-patch to the Func API; parsing RENDERZONE properly but finally inserting the zone at the end of the rendering pipeline
12 Feb 2010 initial release
Dependencies: None
Home page: Foswiki:Extensions/ZonePlugin
Support: Foswiki:Support/ZonePlugin

DBCachePlugin: ZonePlugin not found
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